All of that was understandable when religious and cultural affiliation played a significant, and open, role in public life; and along with that, the direct involvement of said religious organization(s). Try being a Catholic (or, a Jew for that matter) and hold a high ranking position in Toronto back then. Heck, even into the '70s, being a Mason in the Ontario public service was a big hairy deal. In days of yore, government financial support; i.e. taxation, was considerably more narrow. Institutions like schools and hospitals were very much (or, at least, much more) funded by the communities they served.
Canadian constitutional support for parochial schools was a reflect of those times. The politicians didn't want to touch it in 1982 because it was, and remains in most provinces, political kryptonite. Interestingly, the province that was the main beneficiary of said protection has walked away from it.
If people want to support a school that teaches that man walked with the dinosaurs, fill yer boots, but I don't want to pay for it. The issue simmers in Canada, but is at a full boil in the US. As in many cases, they are much more divided than us.